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  • Writer's pictureP.K. Peterson

Preparing for the Twindemic of COVID-19 and the Flu

“Constant, random mutation is the survival mechanism of the microbial world. Like all influenza viruses, H1N1 has the advantage of surprise on its side. We have the advantages of science, and of rational and rigorous investigation, on our side, supported today by tools for data collection, analysis, and communication that are unprecedented in their power.”

- Dr. Margaret Chan, Director-General World Health Organization (2007-2017)

“There’s nothing quite like flu in terms of the risk.”

- Tom Frieden, Director, Center for Disease Control and Prevention (2009-2017)

As readers of past Germ Gem posts know, influenza is always of great concern for the medical community not only because of the high number of hospitalizations and deaths every year due to “seasonal flu” but also because of the possibility that we will face a particularly deadly strain “of pandemic flu” like the one in 1918-1919 that killed more than 50 million people worldwide. This year, there is a sense of heightened urgency in preparing for seasonal flu because of the on-going COVID-19 pandemic. The goal of this Germ Gem post is to provide guidance on how to prepare for seasonal flu in the era of COVID-19.

Recap of 2019-2020 flu season. Seasonal flu does not usually garner many headlines. Yet it is an extremely virulent disease that should be taken seriously. According to the CDC, during the six-month period between October 1, 2019 and April 4, 2020, the flu resulted in 39 million to 56 million illnesses in the United States, with 410,000 to 740,000 hospitalizations, and 24,000 to 62,000 deaths. These numbers are consistent with an “average” flu season in the U.S. The number of known infections from flu during that period is about ten times higher than the number of known cases of COVID-19 to date. However, as of the end of August, the infection fatality rate of last year’s flu was only about one-third that of COVID-19. Nevertheless, this year as we enter the flu season (October through May), we are facing not one but two serious viral respiratory tract infections.

Predictions for the 2020-2021 seasonal flu (a fool’s errand). Predictions about influenza are always rife with uncertainty. What still keeps many expert epidemiologists awake at night is the worry that another pandemic flu is waiting in the wings. As I discussed in my October 5, 2019 Germ Gems post, three of the 20th century flu pandemics, including the 1918-1919 H1N1 pandemic that killed more than 50 million people worldwide, were zoonotic, spillovers from birds into humans. Experts remain concerned because, for the last decade or longer, there have been several virulent avian influenza strains circulating in Asia that pose the threat of another spillover to humans. The good news, however, is that these virulent flu strains haven’t yet ignited another devastating flu pandemic. As we all know, what emerged unexpectedly instead in December 2019 was COVID-19, another zoonotic respiratory infection caused by a novel coronavirus.

Influenza and COVID-19 are both caused by viruses spread primarily by droplets and aerosols generated by coughing and sneezing. Asymptomatic infections are higher in COVID-19 (about 40%) than influenza (5-20%). But asymptomatic carriers can transmit both viruses to others.

One might think that the collision of two serious viral respiratory tract infections, influenza and COVID-19, would represent a “perfect storm.” The experience with seasonal flu in the Southern Hemisphere (where seasonal flu has just about run its course) suggests things may not be as bad as we might fear. South Africa experienced a near-total lack of flu cases this year. And cases of seasonal flu in Argentina, Chile, and Australia are less than 1% of what they were a year ago. The explanation for this dramatic reduction in flu cases in these regions of the world appears to be the effectiveness of measures to prevent COVID-19, e.g., social distancing, wearing masks, and school closures, in protecting against both SARS-CoV-2 and influenza viruses.

Perhaps we, too, can hope to see a very mild seasonal flu season due to simple containment measures used to protect us against SARS-CoV-2. But, don’t bet your life on it. Instead, prepare for this year’s seasonal influenza.

Get Vaccinated. Unlike the situation with COVID-19, there already is a highly safe vaccine against influenza with about 50% efficacy. So, Get Vaccinated!

Who should be vaccinated? Everyone 6 months of-age-or older should be vaccinated, unless there is a contraindication. (At one time, allergy to eggs was a contraindication, but there are now vaccines developed in cell cultures rather than in chicken eggs available for such individuals.) Vaccination should be deferred, however, in those with known or suspected COVID-19. Consult with your doctor about what is recommended for you.

What vaccine should be given? As in past years, the recommended flu vaccine for 2020-2021 contains either three or four influenza A and B strains that were selected based on their prevalence in cases in the Southern Hemisphere. Because older adults often have a blunted immune response to vaccines, there are either high-dose or adjuvanted vaccines available for those over 60 years-of-age that give more robust immune protection. Your doctor can advise you about which vaccine is best for you.

When should you be vaccinated? Now! Don’t wait! The CDC recommends getting vaccinated in September or October.

Where should you get vaccinated? The CDC works closely with public health and healthcare providers on how to vaccinate people against flu without increasing their exposure to SARS-CoV-2. Both Walgreens and CVS Pharmacy have stepped up their supplies of flu vaccine this year; they should be ready for you. You can get more information on where to get a flu vaccine by visiting

Influenza and COVID-19: Know the Symptoms. Along with a long list of other viruses, influenza viruses and SARS-CoV-2 target the respiratory tract. The same people who are most vulnerable to risks from COVID-19, such as the elderly and those with chronic medical conditions, are also at greatest risk of severe or life-threatening influenza. As more has been learned about COVID-19, it appears the symptoms are very similar to influenza. As you can see in the lists below, the only symptom that can distinguish between the two is the loss of smell or taste in a sizable proportion of those with COVID-19.

Flu Symptoms

Influenza can cause mild to severe illness, and at times can lead to death. Flu is different from a cold. It usually comes on suddenly. People who have flu often have some or all of these symptoms:

  • fever or feeling feverish/chills

  • cough

  • sore throat

  • runny or stuffy nose

  • muscle or body aches

  • headaches

  • fatigue (tiredness)

  • some people may have vomiting and diarrhea, though this is more common in children than adults.

COVID-19 Symptoms

People with COVID-19 can have a wide range of symptoms–-ranging from mild symptoms to severe illness. Symptoms may appear 2-14 days after exposure to the virus.

  • fever or chills

  • cough

  • shortness of breath or difficulty breathing

  • fatigue

  • muscle or body aches

  • headache

  • new loss of taste or smell

  • sore throat

  • congestion or runny nose

  • nausea or vomiting

  • diarrhea

How is influenza diagnosed? The overlap of symptoms of influenza and COVID-19 poses a challenge to physicians in distinguishing between them. Patients with influenza typically experience most severe symptoms during the first week of illness, whereas patients with COVID-19 may experience a longer duration of symptoms with a peak during the second or third week of illness. This distinction is unlikely, however, to be of value in sorting out the diagnosis in the early stage of illness caused by either virus.

Before COVID-19 came along, it was generally recommended during the flu season to treat patients with symptoms compatible with influenza with an antiviral drug without obtaining a diagnostic test because waiting for the results would delay treatment. Recently, an FDA Emergency Use Authorization was issued for multiplex assays that simultaneously detect influenza and SARS-CoV-2. If this becomes readily available, it could be a game changer in patient management.

How is influenza treated? There is an effective treatment for the flu. But early treatment is essential. Therefore, everyone who develops symptoms of flu should immediately contact their doctor or healthcare professional. Generally, the antiviral drug options for adults with the flu are oseltamivir (Tamiflu) or baloxavir (Xofluza). These medications also can be considered within family or group settings to prevent the flu. Patients with severe illness should be hospitalized, and special measures may be needed, as in COVID-19, to support the function of vital organs.

Do the right things. If you needed an added reason to wear a mask, practice social distancing, and avoid crowds to prevent COVID-19, now you have it. It looks like you may “kill two birds with one stone,” that is, by taking precautions against COVID-19, you may also protect yourself against influenza. Get yourself vaccinated against the flu as soon as possible, and keep your fingers crossed that a vaccine against COVID-19 will become available in the next six months. And if you develop symptoms of the flu or COVID-19 contact your doctor immediately for advice about diagnostic testing and treatment.

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Sep 02, 2020



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Main Page images courtesy of Shuxian Hu, MD. Dr. Hu is a scientist in the Neuroimmunology Research Laboratory at the University of Minnesota.

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